Ask HN: Call Detection?

Something just struck me when answering the phone just now. I ad to reach over to my Macbook and bring up iTunes and hit stop to kill the web radio. This is a bit of a pain. One of the coolest features demoed for the iPhone debut was its ability to fade out from a song when you clicked the remote and go into a call.

It would be nice if there was some sort of system for globally detecting that a call is happening in your notebook/desktop OS. Apparently, there is some sort of facility like this in iOS 4, since Skype will fade out the music just like the native phone app. Such integration between one's Mac and iPhone over WiFi/Bluetooth would also be an awesome feature, but this is just wishful thinking for now.

I think Nabaztag detects cell phone call emissions. It also occurred to me that stock ringtones should be easily detectable. What about a cheap USB device that's architected so it can't be easily used for recording more than a second of sound, but can reliably recognize a small number of sounds like ringtones, which can activate software on your PC?

EDIT: Thinkgeek has these silly things: http://www.thinkgeek.com/gadgets/cellphone/a150/ Those would be much more useful if they could talk to your smartphone/pc.